Currently, as wireless communication systems used in communication between a plurality of wireless communication apparatuses in a comparatively small area such as at home and office, wireless LAN (Local Area Network) such as IEEE802.11a, IEEE802.11b, IEEE802.11b and Bluetooth has already been practically implemented. Of these, wireless communication systems complying with standards such as IEEE802.11b, IEEE802.11g and Bluetooth using frequency band of 2.4 GHz that is one of the ISM (Industrial Science Medical) bands requiring no radio license are often used.
Further, adaptive communication technologies for carrying out communication efficiently by carrying out communication while adaptively switching between wireless communication systems according to the communication environment, are studied (for example, refer to Patent Document 1). FIG. 1 shows the conventional wireless communication apparatus carrying out the adaptive communication disclosed in Patent Document 1. In FIG. 1, wireless communication apparatus 3000 has IEEE802.11b wireless section 3001, Bluetooth wireless section 3002 and control section 3003, and control section 3003 carries out communication by switching between wireless sections so as to support two types of wireless communication systems, a wireless communication system complying with IEEE802.11b and a wireless communication system complying with Bluetooth, according to the communication environment.
With this kind of adaptive communication technology, a criterion for appropriate switching of wireless communication systems is material, and an estimation value of communication quality is generally used as this criterion. Regarding the estimation method of the communication quality, when communication is carried out using a wireless communication system complying with IEEE802.11b, in the conventional method disclosed in Patent Document 1, the communication quality for IEEE802.11b is estimated by detecting errors in IEEE802.11b or checking the power of the received signal using the received signal of IEEE802.11b. When this communication quality for IEEE802.11b deteriorates, communication is carried out by switching the wireless communication system to Bluetooth that is comparatively robust with respect to radio interference.
Further, when communication is carried out using Bluetooth, a receiving system of IEEE802.11b is also made to simultaneously operate periodically, and communication quality for IEEE802.11b is estimated by detecting errors in IEEE802.11b or checking the power of the received signal using the received signal for IEEE802.11b. When this communication quality for IEEE802.11b is good, communication is carried out by switching the wireless communication system to IEEE802.11b with a larger communication capacity.    Patent Document 1: Japanese Patent Application Laid-Open No. 2003-199160.